连续玄武岩纤维及其复合材料耐腐蚀特性

通过考察玄武岩纤维在蒸馏水、氢氧化钠溶液及盐酸中煮沸3h后的强度与质量变化,及其复合材料在8种化学介质中分别浸泡15d、30d和90d后的力学性能与表面形态变化,对一种国产连续玄武岩纤维及其复合材料的耐化学介质腐蚀性能进行了实验研究.结果表明,该玄武岩纤维及其复合材料都有很好的耐水及耐碱性能,且纤维的耐碱性能优于其耐酸性能.由于玄武岩纤维的耐酸碱性能差异,使复合材料具有如下腐蚀特性:酸性介质中,复合材料弯曲强度和弯曲模量同步降低;碱性介质中,复合材料弯曲强度降低,而弯曲模量几乎保持不变.      

喷丸对18％Ni型超高强度钢低周疲劳性能影响

对C250型18%Ni超高强度钢（C250钢）进行铸钢丸一次喷丸（单喷）和铸钢丸+玻璃丸二次喷丸（双喷）,研究喷丸前后的表面形貌、显微组织和低周疲劳性能的变化.结果表明,单喷后C250钢低周疲劳寿命提高了接近2.5倍,而双喷后试样疲劳寿命提高3倍.喷丸表面的亚晶粒细化是提高低周疲劳性能的主要因素,二次喷丸带来的平滑化效果进一步提高了低周疲劳性能.平滑化效果减小了表面应力集中程度,使经过双喷后试样疲劳断口为单源疲劳断口,而未喷丸试样和单喷试样的低周疲劳断口呈现多源疲劳状态.     

齿轮测量中心测头数据采集系统

提出了齿轮测量中心电感测头的新型数据采集系统,包括以集成开关构成的新型相敏检波器和以单片机为核心的数据采集系统,可以应用于各种电感信号的处理,具有较强的通用性。     

Tropospheric wet refractivity tomography using multiplicative algebraic reconstruction technique

Algebraic reconstruction techniques (ART) have been successfully used to reconstruct the total electron content (TEC) of the ionosphere and in recent years be tentatively used in tropospheric wet refractivity and water vapor tomography in the ground-based GNSS technology. The previous research on ART used in tropospheric water vapor tomography focused on the convergence and relaxation parameters for various algebraic reconstruction techniques and rarely discussed the impact of Gaussian constraints and initial field on the iteration results. The existing accuracy evaluation parameters calculated from slant wet delay can only evaluate the resultant precision of the voxels penetrated by slant paths and cannot evaluate that of the voxels not penetrated by any slant path. The paper proposes two new statistical parameters Bias and RMS, calculated from wet refractivity of the total voxels, to improve the deficiencies of existing evaluation parameters and then discusses the effect of the Gaussian constraints and initial field on the convergence and tomography results in multiplicative algebraic reconstruction technique (MART) to reconstruct the 4D tropospheric wet refractivity field using simulation method.     

Predicting performance in manually controlled rendezvous and docking through spatial abilities

Manually controlled rendezvous and docking (manual RVD) is a challenging space task for astronauts. This study aims to identify spatial abilities that are critical for accomplishing manual RVD. Based on task analysis, spatial abilities were deduced to be critical for accomplishing manual RVD. 15 Male participants performed manual RVD task simulations and spatial ability tests (the object-manipulation spatial ability and spatial orientation ability). Participants’ performance in the test of visualization of viewpoints (which measures the spatial orientation ability) was found to be significantly correlated with their manual RVD performance, indicating that the spatial orientation ability in the sense of perspective taking is particularly important for accomplishing manual RVD.     

Stability of relative equilibria of the full spacecraft dynamics around an asteroid with orbit–attitude coupling

The full dynamics of spacecraft around an asteroid, in which the spacecraft is considered as a rigid body and the gravitational orbit–attitude coupling is taken into account, is of great value and interest in the precise theories of the motion. The spectral stability of the classical relative equilibria of the full spacecraft dynamics around an asteroid is studied with the method of geometric mechanics. The stability conditions are given explicitly based on the characteristic equation of the linear system matrix. It is found that the linearized system decouples into two entirely independent subsystems, which correspond to the motions within and outside the equatorial plane of the asteroid respectively. The system parameters are divided into three groups that describe the traditional stationary orbit stability, the significance of the orbit–attitude coupling and the mass distribution of the spacecraft respectively. The spectral stability of the relative equilibria is investigated numerically with respect to the three groups of system parameters. The relations between the full spacecraft dynamics and the traditional spacecraft dynamics, as well as the effect of the orbit–attitude coupling, are assessed. We find that when the orbit–attitude coupling is strong, the mass distribution of the spacecraft dominates the stability of the relative equilibria; whereas when the orbit–attitude coupling is weak, both the mass distribution and the traditional stationary orbit stability have significant effects on the stability. We also give a criterion to determine whether the orbit–attitude coupling needs to be considered.     

Satellite-observed biological variability in the equatorial Pacific during the 2009–2011 ENSO cycle

The event of 2009–2011 El Niño Southern Oscillation (ENSO) provides an opportunity to gain insight into the biological variability of the equatorial Pacific Ocean for an entire ENSO cycle with satellite and in situ observations. Even though El Niño and La Niña in general led to respectively weakened and enhanced chlorophyll-a concentration and net primary production (NPP) along the equatorial Pacific Ocean during the 2009–2011 ENSO cycle, biological responses were highly disparate along the equator and attributed to different driving mechanisms. In the eastern equatorial Pacific east of 150°E, the El Niño-La Niña biological change was in general small except for the transition period even though sea surface temperature (SST) showed over ∼5 °C drop from El Niño to La Niña. In the central-eastern (170°W–140°W) equatorial Pacific, moderate change of biological activity is attributed to the changes of thermocline driven by the eastward propagating equatorial Kelvin waves and changes of zonal currents and undercurrents. Highest biological response in this ENSO cycle was located in the central (170°E–170°W) and central-western (150°E–170°E) equatorial Pacific with quadruple chlorophyll-a concentration and over ∼400 mg C m⁻² d⁻¹ increase of NPP from El Niño in 2009 to La Niña in 2010. However, spatial pattern of ENSO biological variability as represented with NPP is not exactly the same as chlorophyll-a variability. Wind-driving mixing of nutrients and eastward advection of the oligotrophic warm pool waters are attributed to this significant biological variability in this region.     

基于边频相对能量和的柱塞泵磨损状态识别

摩擦磨损是飞机柱塞泵典型的渐进性故障,因磨损量难以直接测量,通常采用振动信号进行间接测量.磨损引起的振动信号故障特征微弱,对磨损状态进行准确地识别比较困难.针对上述问题,提出了基于谐波分量边频相对能量和的磨损状态识别方法,该方法对壳体振动信号进行Hilbert包络解调消除高频周期干扰,得到清晰的谐波分量,在各谐波分量的特定边频区间内计算最大能量与平均能量的比值并求和,将该值作为新的特征量来表征柱塞泵的不同磨损状态,利用网格法对边频区间范围寻优.结果表明,边频相对能量和相比传统的特征频率能量对磨损状态的区分度更高,适于磨损状态识别.      

UHMWPE/PCH复合材料性能研究

采用超高分子量聚乙烯(UHMWPE)纤维作增强材料,结构与UHMWPE纤维相似、且对纤维表面具有良好润湿性的全碳氢树脂(PCH)作基体,通过热压成型工艺制备UHMWPE/PCH复合材料,并通过扫描电镜、介电谱仪等方法对复合材料的力学性能、介电性能、吸水、湿热性能及界面粘接性能进行表征.结果表明,UHMwPE/PCH复合材料力学性能良好、介电性能优异、吸水率小、吸湿率低、粘接性能好.     

多层缝隙耦合贴片型频率选择表面研究

设计了一种基于缝隙耦合的贴片型频率选择表面（Frequency selective surfaces, FSS）,该FSS拥有窄带特性。分析了缝隙结构对FSS的频率响应的影响,提出 了一种具有极化稳定性和角度稳定性的双极化FSS单元。采用全波电磁仿真软件对其进行分 析,同时采用谱域法和周期性矩量法对该FSS进行了理论分析并得到解析解。通过将缝隙改 为十字缝隙实现双极化设计,仿真结果显示该结构具有极化稳定性和角度稳定性,并与理论 分析吻合,表明设计的正确性。